“Cutting six-day delivery is not a viable plan for the future,” he said in a statement Wednesday. “It will lead to a death spiral that will harm rural America while doing very little to improve the financial condition of the Postal Service.”

Sanders argued that providing fewer services would drive away customers and that rural residents, businesses, senior citizens and veterans would be hurt by the change.

The Postal Service said Wednesday that it plans to cut back to five-day-a-week deliveries for everything except packages starting in August. The Postal Service, which suffered a $15.9 billion loss in the past budget year, said cutting Saturday delivery should save $2 billion annually.

Package delivery has increased by 14 percent since 2010, officials say, while the delivery of letters and other mail has plummeted. Email has reduced the mailing of paper letters, but online purchases have increased package shipping.

Congress has voted in the past to block the elimination of Saturday delivery, and Wednesday’s announcement immediately drew protests from some lawmakers. The plan also brought vigorous objections from farmers, the letter carriers’ union and others.

Last year, Sanders drafted a measure reversing a 2006 requirement that the Postal Service pre-fund 75 years of retiree health benefits over a 10-year period, a requirement he said accounts for 80 percent of Postal Service debt since 2007. The House did not consider the bill, according to Sanders.

Tom Rizzo, a spokesman for the Postal Service in northern New England, said the elimination of Saturday delivery would not affect the Saturday hours at Vermont post offices. He stressed that the offices would remain open Saturdays for retail window services and picking up from rented postal boxes.

Rizzo said the need for mail carriers would be “significantly reduced” as a result of the change, but that any workforce reduction would happen over time, through attrition.

“We are currently working to define the employee impact and will be meeting with our unions and management associations to discuss the employee impact in accordance with our collective bargaining agreements,” Rizzo wrote in an email.

“The Postal Service has a proven track record of working with affected employees,” he said. “In fact, the Postal Service has reduced over 193,000 career positions since 2006 without major layoffs.”

A call to Robert Broxton, president of the National Postal Mail Handlers Union Local 301, which covers Maine, New Hampshire, Vermont, Rhode Island, Massachusetts and most of Connecticut, was not immediately returned Wednesday.